Flame photometry is an atomic emission method for the routine detection of metal salts, principally Na, K, Li and Ca. Quantitative analysis of these species is performed by measuring the flame emission of solutions containing the metal salts. Solutions are aspirated into the flame. The hot flame evaporates the solvent, atomizes the metal, and excites a valence electron to an upper state. Light is emitted at characteristic wavelengths for each metal as the electron returns to the ground state. Optical filters are used to select the emission wavelength monitored for the analyte species. Comparison of emission intensities of unknowns to either that of standard solutions, or to those of an internal standard, allows quantitative analysis of the analyte metal in the sample solution.
Flame photometry is a simple, relatively inexpensive, high sample throughput method used for clinical, biological, and environmental analysis. The low temperature of the natural gas and air flame, compared to other excitation methods such as arcs, sparks, and rare gas plasmas, limit the method to easily ionized metals. Since the temperature isn't high enough to excite transition metals, the method is selective toward detection of alkaline and alkali earth metals. On the other hand, the low temperatures renders this method susceptible to certain disadvantages, most of them related to interference and the stability (or lack thereof) of the flame and aspiration conditions. Fuel and oxidant flow rates and purity, aspiration rates, solution viscosity, concomitants in the samples, etc affect these. It is therefore very important to measure the emission of the standard and unknown solutions under conditions that are as nearly identical as possible.
Flame photometry is still one of the most demanded analytical techniques by chemists working in various industrial, agricultural and clinical fields. It is a low-cost alternative to the Ion Selective measurement method and provides the chemist with an acceptable detection limit when measuring Sodium, Potassium, Lithium and Calcium in aqueous samples. Sedico Ltd. propose two instruments, the AFP 45 flame photometer and the multi-channel automatic AFP 100 for the simultaneous analysis of Sodium, Potassium, Lithium and Calcium in one sample aspiration. The details are in the relevant sections of this page.